Add CONNECTIVITY_INTERNAL permission

Bluetooth tethering still needs to call some
NetworkManagementService APIs that are protected by
CONNECTIVITY_INTERNAL. But this permission has been removed from
bluetooth package by mistake, add permission back for using
those APIs normally.

Bug: 32963470
Test: Verify bluetooth tethering manually.
Change-Id: I96d9aec3fda2600b60e9ca85d5cbf53b4d2a1ead